This is not due to a medical need. Female-to-male strap-on pornography became a popular sub-genre in the United States in the early 21st century, with a number of studios producing dedicated series about it. The surfacing of sex tapes has become so common that some are leaked as a marketing tool to advance or establish a media career. Bondage is usually, but not always, a sexual practice. Masturbation involves touching, pressing, rubbing or massaging a person genital area, either with the fingers or against an object such as a pillow; inserting fingers or an object into the anus ; and stimulating the penis or vulva with an electric vibrator, which may also be inserted into the vagina or anus. As observation is encouraged, voyeurism and exhibitionism are closely associated with dogging. Not all crush fetishists are that extreme! Although macrophilia literally translates to simply a lover of large, in the context of a sexual fantasy it is used to mean someone who attracted to beings larger than themselves. The effect is to give the viewer the sense that they are experiencing the sex acts that they are watching, as opposed to simply watching others as a voyeur. Weather Report Girl is considered yuri hentai in English usage for its depiction of lesbian sex, but in Japan it is just yuri. The principal characteristic of voyeurism is that the voyeur does not normally interact directly with the subject of his/her interest, who is often unaware of being observed. The most established and probably most cliche set form of dominance and submission is Dominance and slavery. Bukkake videos are a relatively prevalent niche in contemporary pornographic films. In terms of physical pleasure, a woman genitals may get celebrity porn stars direct stimulation from the base of the dildo, or in the case of a double-ended dildo, from vaginal penetration. For example, the Kama Sutra, in particular, goes into specific detail on how to properly strike a partner during sex. This yields a view that would not be obtainable directly through the eyes of a person while experiencing the sex act.